Add WriteWithChanges() method (#2)

Author: ryanclark

vt.go

@@ -19,6 +19,9 @@ type Terminal interface {
 	// buffer empties. State is locked as soon as first rune is read, and unlocked
 	// when buffer is empty.
 	Parse(bf *bufio.Reader) error
+
+	// WriteWithChanges writes terminal changes to state and returns the line numbers that changed.
+	WriteWithChanges(p []byte) ([]int, error)
 }
 
 // View represents the view of the virtual terminal emulator.

vt_other.go

@@ -56,6 +56,36 @@ func (t *terminal) Write(p []byte) (int, error) {
 	return written, nil
 }
 
+// WriteWithChanges writes to the terminal state and returns the line numbers that changed.
+func (t *terminal) WriteWithChanges(p []byte) ([]int, error) {
+	var dirtyLines = make(map[int]bool)
+	var written int
+	r := bytes.NewReader(p)
+	t.lock()
+	defer t.unlock()
+	for {
+		c, sz, err := r.ReadRune()
+		if err != nil {
+			if err == io.EOF {
+				break
+			}
+			return nil, err
+		}
+		written += sz
+		if c == unicode.ReplacementChar && sz == 1 {
+			if r.Len() == 0 {
+				// not enough bytes for a full rune
+				return nil, nil
+			}
+			t.logln("invalid utf8 sequence")
+			continue
+		}
+		t.put(c)
+		dirtyLines[t.cur.Y] = true
+	}
+	return uniqueSorted(dirtyLines), nil
+}
+
 // TODO: add tests for expected blocking behavior
 func (t *terminal) Parse(br *bufio.Reader) error {
 	var locked bool

vt_posix.go

@@ -6,6 +6,7 @@ import (
 	"bufio"
 	"bytes"
 	"io"
+	"slices"
 	"unicode"
 	"unicode/utf8"
 )
@@ -57,6 +58,61 @@ func (t *terminal) Write(p []byte) (int, error) {
 	return written, nil
 }
 
+// WriteWithChanges writes to the terminal state and returns the line numbers that changed.
+func (t *terminal) WriteWithChanges(p []byte) ([]int, error) {
+	var dirtyLines = make(map[int]bool)
+	r := bytes.NewReader(p)
+	t.lock()
+
+	prevRow := t.cur.Y
+
+	defer t.unlock()
+	for {
+		c, sz, err := r.ReadRune()
+		if err != nil {
+			if err == io.EOF {
+				break
+			}
+			return uniqueSorted(dirtyLines), err
+		}
+		if c == unicode.ReplacementChar && sz == 1 {
+			if r.Len() == 0 {
+				return uniqueSorted(dirtyLines), nil
+			}
+			t.logln("invalid utf8 sequence")
+			continue
+		}
+
+		beforeRow := t.cur.Y
+		t.put(c)
+		afterRow := t.cur.Y
+
+		dirtyLines[beforeRow] = true
+		if afterRow != beforeRow {
+			dirtyLines[afterRow] = true
+		}
+
+		if t.cur.Y != prevRow {
+			prevRow = t.cur.Y
+		}
+	}
+
+	return uniqueSorted(dirtyLines), nil
+}
+
+func uniqueSorted(m map[int]bool) []int {
+	lines := make([]int, 0, len(m))
+	for line := range m {
+		lines = append(lines, line)
+	}
+	if len(lines) == 0 {
+		return lines
+	}
+
+	slices.Sort(lines)
+	return lines
+}
+
 // TODO: add tests for expected blocking behavior
 func (t *terminal) Parse(br *bufio.Reader) error {
 	var locked bool